The LHC collimation system has been re-designed over in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a final approach for collimation and cleaning has been adopted. In total 132 pure collimator locations have been reserved in the two LHC rings and can be installed in a phased approach. Up to 88 collimators of five different types will be available for initial beam operation. The system has been fully optimized for avoiding beam-induced quenches of superconducting magnets and for sufficient survival of beamline components against radioactive dose. The phased approach for LHC collimation is described, the various collimators and their functionalities are explained, and the expected system performance is summarized

Aberle, O.

Assmann, R.

Baishev, I.

Bellodi, G.

Bertarelli, A.

Bracco, C.

Braun, H.

Brugger, M.

Calatroni, S.

Chamizo, R.

Dallochio, A.

Dehning, B.

Ferrari, A.

Gander, P.

Grudiev, A.

Holzer, E.B.

Jeanneret, J.B.

Jimenez, J.M.

Jonker, M.

Kadi, Y.

Kershaw, K.

Kurochkin, I.

Lendaro, J.

Lettry, J.

Losito, R.

Magistris, M.

Masi, A.

Mayer, M.

Métral, E.

Perret, R.

Rathjen, C.

Redaelli, S.

Robert-Demolaize, G.

Roesler, S.

Ruggiero, F.

Santana, M.

Sievers, P.

Sobczak, M.

Tsoulou, K.

Vlachoudis, V.

Weiler, T.

Assmann, R W

Aberle, O

Bellodi, G

Bertarelli, A

Bracco, C

Braun, H

Brugger, M

Calatroni, S

Chamizo, R

Dallocchio, Alessandro

Dehning, B

Ferrari, A

Gander, P

Grudiev, A

Holzer, E B

Jeanneret, J B

Jiménez, J M

Jonker, M

Kadi, Y

Kershaw0, K

Lendaro, J

Lettry, Jacques

Losito, R

Magistris, M

Masi, A

Mayer, M

Métral, E

Perret, R

Rathjen, C

Redaelli, S

Robert-Démolaize, G

Roesler, S

Ruggiero, F

Santana, M

Sievers, P

Sobczak, M

Tsoulou, A

Vlachoudis, V

Weiler, T

Baishev, I S

Kurochkin, I

CERN Document Server

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHEuropean Laboratory for Particle PhysicsTHE FINAL COLLIMATION SYSTEM FOR THE LHCThe LHC collimation system has been re-designed over in order to address the unprecedented challenges thatare faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a final approachfor collimation and cleaning has been adopted. In total 132 pure collimator locations have been reserved inthe two LHC rings and can be installed in a phased approach. Up to 88 collimators of five different typeswill be available for initial beam operation. The system has been fully optimized for avoiding beam-inducedquenches of superconducting magnets and for sufficient survival of beamline components against radioactivedose. The phased approach for LHC collimation is described, the various collimators and their functionalitiesare explained, and the expected system performance is summarized.Large Hadron Collider ProjectAbstractR. Assmann, O. Aberle, I. Baishev1), G. Bellodi, A. Bertarelli, C. Bracco, H. Braun, M. Brugger, S. Calatroni, R. Chamizo, A. Dallochio, B. Dehning, A. Ferrari, P. Gander, A. Grudiev,E. B. Holzer,  J.B. Jeanneret, J.M. Jimenez, M. Jonker, Y. Kadi, K. Kershaw, I. Kurochkin1), J. Lendaro, J. Lettry, R. Losito, M. Magistris, A. Masi, M. Mayer, E. Métral, R. Perret,C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, F. Ruggiero, M. Santana, P. Sievers,M. Sobczak, K. Tsoulou, V. Vlachoudis, T. WeilerLHC Project Report 919CERN,CH-1211 Geneva 23,SwitzerlandGeneva, June 20061) IHEP, Protvino, RussiaCERN, Geneva, SwitzerlandPresented atEPAC'06, Edinburgh, UK, June 26-30, 2006THE FINAL COLLIMATION SYSTEM FOR THE LHC R. Assmann, O. Aberle, G. Bellodi, A. Bertarelli, C. Bracco, H. Braun, M. Brugger,  S. Calatroni, R. Chamizo, A. Dallochio, B. Dehning, A. Ferrari, P. Gander, A. Grudiev,  E. B. Holzer, J.B. Jeanneret, J.M. Jimenez, M. Jonker, Y. Kadi, K. Kershaw, J. Lendaro, J. Lettry, R. Losito, M. Magistris, A. Masi, M. Mayer, E. Métral, R. Perret, C. Rathjen, S. Redaelli, G. Robert-Demolaize, S. Roesler, F. Ruggiero, M. Santana, P. Sievers, M. Sobczak, K. Tsoulou,  V. Vlachoudis, T. Weiler, CERN, Geneva, Switzerland I. Baishev, I. Kurochkin,  IHEP, Protvino, Russia Abstract The LHC collimation system has been re-designed over in order to address the unprecedented challenges that are faced with the 360 MJ beams at 7 TeV. The layout of the LHC has now been frozen and a final approach for colli-mation and cleaning has been adopted. In total 132 pure collimator locations have been reserved in the two LHC rings and can be installed in a phased approach. Up to 88 collimators of five different types will be available for initial beam operation. The system has been fully opti-mized for avoiding beam-induced quenches of super-conducting magnets and for sufficient survival of beam-line components against radioactive dose. The phased approach for LHC collimation is described, the various collimators and their functionalities are explained, and the expected system performance is summarized. INTRODUCTION Nominal luminosity of the LHC requires the storage and collision of 7 TeV beams with each 360 MJ of stored energy [1,2]. It is shown in Fig. 1 that this is about 200 times more than handled in present accelerators. The energy density at the LHC collimators reaches 1 GJ/mm2.  The LHC must handle unavoidable beam intensity losses. Allowing for a peak loss of 1% of the beam within 10 s, a peak power load of 500 kW must be handled at 7 TeV [1]. At the same time no super-conducting (SC) magnet may be exposed to an energy deposition of more than 8.5 W/m, otherwise it would quench. The LHC col-limation system is designed to intercept beam losses and to absorb them in the dedicated cleaning insertions in IR3 and IR7 [2]. Only a small fraction of lost protons (less than 10-3) is allowed to escape the cleaning insertions. The cleaning performance is described more precisely by a local inefficiency η c which is the ratio of number Ni of protons lost at any location of the ring in a given bin of length Li over the total number Ntot of protons lost: ictot iNN Lη =⋅                             (1) The required local cleaning inefficiency at 7 TeV is about 2×10-5 m-1 for nominal intensity of 3×1014 p per beam. This value allows an indicative comparison (the precise quench limit in the LHC depends on the magnet type and the geometry and time structure of losses). 0.010.111010010000.1 1 10 100 1000 10000Stored beam energy [MJ]Beam momentum [GeV/c]SNSISRLEP2SppSLHC(top)LHC(inj)SPS HERATEVATRON Figure 1: Stored beam energy versus beam momentum for various past, present and future high power accelerators. COLLIMATION DESIGN The LHC collimation system has been re-designed [2] with the following major goals: 1. Robustness of collimators [3, 4] against the speci-fied regular beam losses (500 kW over 10 s) [1] and accident scenarios (2 MJ shock impact in 200 ns) [5]. 2. Excellent cleaning inefficiency (2×10-5 m-1) [2]. 3. Minimized impedance with collimation gaps of down to 2.5 mm and a total installed collimator jaw length of about 48 m per beam [6, 7]. 4. Adequate tolerances for mechanical parts (e.g. jaw flatness) and actuation (e.g. precise motors) for avoiding loss of efficiency due to imperfections [3]. 5. Integration of the collimator with the existing ma-chine infrastructure, including radiation optimiza-tion for fast handling of radioactive collimators [8]. The collimation layout is by now frozen for the LHC. It implements a phased approach. For the two beams there are in total 152 locations allocated to LHC collimators and absorbers. 14 of these locations are for transfer line collimators. The first phase of LHC collimation will in-clude 88 ring collimators with a total beam intensity lim-ited to less than 40% of the nominal intensity. A further 34 ring locations are equipped and ready for an upgrade with advanced collimators around the year 2010. Finally, 16 locations are reserved for ultimate efficiency, however, are not equipped with any infrastructure. The collimation layout during the initial phase of LHC collimation is summarized in Fig. 2. Several families of collimators have been integrated for 3-4 stage cleaning and absorption.    Figure 2: Layout for LHC collimation during phase 1. Red labels are beam 1 collimators; black labels beam 2).   Figure 3: Proton loss pattern for 7 TeV beam 1 betatron collimation, for zero orbit (top) and a worst phase 4 mm static orbit (bottom). Blue bars indicate losses in SC ele-ments, red in warm elements and green in collimators. Here we shortly describe the major LHC collimators: 1. Primary collimators (TCP) with robust CFC jaws [3, 4] for interception of primary beam halo. 2. Secondary collimators (TCSG) with robust CFC jaws [3, 4] for interception of secondary beam halo. 3. Tungsten based absorbers (TCLA) at the end of the cleaning insertions for protecting the SC arcs. 4. Tungsten based absorbers (TCT) for protection and cleaning at the triplets in the experimental insertions. Several other collimators play an important role for lo-cal protection against injection and dump problems [5]. Upgrade collimators are not included in Fig. 2. PERFORMANCE  The required settings of collimators and absorbers were worked out in detail and the multi-turn performance of the collimation system was studied in detail [7].  Figure 4: A view of a series TCS collimator during pro-duction. Both jaws and RF contacts have been mounted.  Simulations track 5 million halo protons for 200 turns with physical interactions in all collimators and absorbers, predicting losses in a detailed LHC aperture model [9, 10]. Studies were done for different energies, various col-limation settings and for several imperfections [10, 11]. An example loss map is shown in Fig. 3 for zero and per-turbed orbit. Independently collimator-induced impedance was studied [7]. It was found that the initial collimation system (phase 1) might be limited by several effects: 1. The total LHC impedance is strongly dominated by collimators [6, 7]. The collimator-induced imped-ance is expected to limit the total intensity to about 30-40% of its nominal value, if octupoles are fully powered.  2. The collimation efficiency and energy deposi-tion [12] is compatible with about 40% of nominal intensity for protons. However, it is expected that imperfections will reduce the collimation efficiency by a factor 2-4 [11]. For ions it is expected that an in-tensity of about 50% of nominal can be reached [13]. 3. The jaws will experience long term damage due to beam-loss induced radiation [14]. An upgrade of the system and the R&D on advanced collimators is therefore an integral part of the LHC colli-mation system. Ring locations have been already fully equipped for this mandatory upgrade. DESIGN, PRODUCTION, INSTALLATION The first phase of LHC collimation requires 8 different types of collimators and various masks. Major design work has been completed, prototyping and beam tests were successful [4] and series production has started. Fig. 4 shows the photograph of a secondary ring collima-tor during series production. The two CFC jaws are visi-ble, as are the transverse and longitudinal RF fingers. Heavy cooling on the collimator jaws and the tank ensure full functionality for the peak beam loss rates.  Figure 5: Integration study for ring collimators with all required infrastructure in the LHC tunnel.   Figure 6: Photograph of an installed ring collimator on its quick plug-in support in IR8 of the LHC. The first collimators have been installed into the LHC tunnel. The collimator tanks have been integrated with radiation-optimized quick plug-in supports (water and controls passes through quick plugs), quick connection flanges, the second beam pipe, vacuum pumping stations, beam loss monitors and water connections. This is illus-trated in Fig. 5 for a series of 4 collimators. A photograph of the first installed ring collimator in IR8 of the LHC is shown in Fig. 6. The first installation was completed in less than 10 minutes. CONCLUSION The collimation system has been re-designed over the last 3 years to address the challenges of the LHC. A pow-erful system has been implemented, including up to 152 collimators for the two rings. Initially up to 102 collima-tors will be used to extend the state-of-the-art in handling of stored energy in super-conducting rings from presently 2 MJ to 40-100 MJ. The important collimator designs for this initial system have been worked out, successfully tested, series production of 125 collimators has started and the first collimators have been installed into the LHC. Collimators and machine layout have been optimized for radiation impact and collimators were integrated with important beam instrumentation and infrastructure. The LHC collimation system includes 34 fully equipped ring locations for an upgrade with advanced collimators around 2010. It is the goal that the upgraded system will allow nominal intensities in the LHC, bring-ing the state-of-the-art to 360 MJ and energy density at collimators to 1 GJ/mm2. Final design choices and deci-sions for the upgrade will be based on the experience with the LHC beams and the initial collimation system. If re-quired, an additional 16 collimators can be installed into non-equipped but reserved LHC locations. REFERENCES [1] R. Assmann et al: “Requirements for the LHC colli-mation system”. Proc. EPAC 2002. CERN-LHC-Project-Report-599. [2] “The LHC design report, Vol.I Chapter 18”. CERN-2004-003. [3] A. Bertarelli et al: “Mechanical Design for Robust-ness of the LHC Collimators”. Proc. PAC05. [4] O. Aberle et al: “LHC Collimation : Design and Re-sults from Prototyping and Beam Tests”. Proc. PAC05. CERN-LHC-Project-Report-850. [5]  B. Goddard et al: “Protection of the LHC against Unsynchronised Beam Aborts”. TUPLS013. These proceedings. [6] H. Burkhardt et al: “Measurements of the LHC Col-limator Impedance with Beam in the SPS”. Proc. PAC05. CERN-LHC-Project-Report-831. [7] E. Metral et al: “Overview of Impedance and Single-Beam Instability Mechanisms”. Proc. PAC05. CERN-AB-2005-041.  [8] M. Brugger et al: “Calculation of Residual Dose Rates and Intervention Scenarios for the LHC Beam Cleaning Insertions - Constraints and Optimization”. Proc. PAC 2005. [9] G. Robert-Demolaize et al: “A New Version of Six-Track with Collimation and Aperture Interface”. Proc. PAC05. CERN-AB-2005-033. [10] G. Robert-Demolaize et al: “Critical halo Loss Loca-tions in the LHC”. TUPLS019. These proceedings. [11] C. Bracco et al: “LHC Collimation Efficiency during Commissioning”. TUPLS018. These proceedings. [12] V. Vlachoudis et al: “Energy Deposition Studies for the Betatron Cleaning Insertion”. Proc. PAC05. CERN-LHC-Project-Report-825. [13] H. Braun et al: “Collimation of Heavy Ion Beams in LHC”. Proc. EPAC04. CERN-LHC-Project-Report-766. [14] N. Simos. Private communication. 

The final collimation system for the LHC

PORTO Publications Open Repository TOrino

The LHC collimation system has been re-designed over
in order to address the unprecedented challenges that are
faced with the 360 MJ beams at 7 TeV. The layout of the
LHC has now been frozen and a final approach for collimation
and cleaning has been adopted. In total 132 pure
collimator locations have been reserved in the two LHC
rings and can be installed in a phased approach. Up to 88
collimators of five different types will be available for
initial beam operation. The system has been fully optimized
for avoiding beam-induced quenches of superconducting
magnets and for sufficient survival of beamline
components against radioactive dose. The phased
approach for LHC collimation is described, the various
collimators and their functionalities are explained, and the
expected system performance is summarized

The final collimation system for the LHC

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